We plan to study the determinants of the distribution of the blood pressure in children and adolescents and the relationship between blood pressure and certain biological and social characteristics during adolescence to the blood pressure of adults 15-20 years later. Four population groups will be studied: 1. Newborns to the first two years of life, 2. A low-income, predominately black housing development, Terrace Village, 3. An upper-income school district, Upper St. Clair, 4. A follow-up of high school students in Dormont, Pennsylvania, originally examined in 1956-61. The major hypotheses to be tested are that the distribution of blood pressure is a function of host and environmental factors of which obesity and salt intake are the major determinants; that individual variability of blood pressure (biological variations) may both obscure true relationships and be an important determinant of blood pressure. We also will attempt to determine whether elevated pulse rate during the first few years of life is a precursor of subsequent elevated blood pressure or hypertension within families.